The present invention relates to a process for preparing improved foamable synthetic resin granules by suspension polymerization.
The present commercial foamable synthetic resin granules, such as foamable styrene resin, have one or more of the following disadvantages:
I. Cells in a section of foamed resin granules are very coarse, when the resin granules are foamed immediately after preparation. A period of aging for several days or one month is necessary.
II. Cells in a section of foamed resin granules are very coarse, when the resin granules are foamed after being exposed to high temperatures.
III. Cells in a section of foamed resin granules are very coarse, when the foamable resin granules are kept (without foaming) until fine cells become obtainable in foamed resin granules, and then are exposed to high temperatures, such as those of the summer season, and then the resin granules are foamed.
IV. Resin granules are prone to cause blocking in a foaming machine.
V. A long time is required to cool a molded shaped article heated in a die, when foamed resin granules are poured into a large die to obtain a special large molded shaped article.